Diesel fuel ignition promoter



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Patented Dec. 24, 1940 Pharis Miller, Des Moines, Iowa, and Gould H'. Cloud, Elizabeth, N. J.,'assignors to Standard Oil Development Company, a corporation of Delaware No Drawing. Application July 23, 1938, Serial No. 221,014

6 Claims. (01. 44-9) This invention has as its chief object the improvement of fuels for use in compression-igni tion engines and relates particularly to the use' of novel'addition agents for improving the ignitionqualities of hydrocarbon fuels when they undergo combustion in such engines of the high speed Diesel type. i

In consideration of increasing the power and fuel economy in the operation of compressionignition engines, principally when the hydrocarbon fuel contains insufficient amounts of hydrocarbon compounds recognizable as serving these ends by virtue of their suitable ignition qualities,

the additions of various oxygenand nitrogencontaining organic posed.

Hydrocarbon compounds characterized by aromatic hydrocarbons have poor ignition qualities which give rise to the vibrations manifested by knocking and result in a loss of power. A poor ignition quality in a fuel is most frequently exhibited by an excessive ignition lag, in other words, an excessive delay between the beginning of fuel injection into the combustion chamber compounds have been proof an engine'and the point at which ignition of the injected fuel sets in. On the other hand. normal aliphatic hydrocarbons have good ignition qualities. Normal cetane, in particular, which serves as a standard of high ignition quality in Diesel fuel rating by recommendation of the S. A. E. Volunteer Group for compression-ignition fuel research, has a very short ignition lag. The ignition lag of a fuel consisting of cetane and alphamethyl-naphthalene is shortened very nearly in proportion to the increase in the percentage of cetane by volume in 'such a blend, and when small amounts of addition agents improve the performance of a fuel in the same respect comparable to the improvement made by an increase of about or more of cetane in a blend with alphamethyl-naphthalene, such addition agents have been considered as having commercial significance.

The novel addition agents of this invention are characterized by organic compounds having a diazo group and carboxy group in the same molecule to activate the diazo group by lowering its stability, the carboxy radical being preferably in an acetoxy or acetic acid radical adjacent to the diazo group. Dissolving of small quantities of this type of compound in hydrocarbon fuels for imparting better ignition qualities to the fuels constitutes a more specific object of this invention.

Classes of compounds characterized by an activated diazo group are exemplified by (l) diazo aceticesters and acids, (2) diazo aceto acetic esters, (3) diazo acetic acid salts, and (4) the isomers and polymers of these classes of compounds. ,To these classes of compounds have beenassigned some of the following structural formulae in which R represents generally organic groups containing hydrogen and carbon but preferably an alkyl group such as ethyl, propyl, and higher homologous groups, their isomers, and olefinic analogues:

v 1, Alicyclic diazo acetates:

Ethyl diazo acetate, NzCHCOzCzHs Alpha-diazo-propionic ester,

CHsCCfizHS 2. Diazo-aceto-acetic esters:

- s. Diazo-acetic acid salts;

, I I? HZ(CN: COR)Q and such salts of other metals.

4. (a) Isomers: Iso-diazo-acetic ester:

EN 0 ll CH.COOH

CHCOOR diazo group'linked to an activating acetic acid GTI 2 or acetoxy radical in raising the cetane number of a hydrocarbon fuel is illustrated by the following tabulated results from a comparison of tests on samples of an unmodified hydrocarbon fuel oil with samples of the same fuel oil modified by small amounts of adiazo acetic ester.

Fuel tests Percentage of ethyl diam acetate in a octane Cetane gg? No. Colombian gas oil inmse The method of testing used is described in the S. A. E. Journal of June, 1936, page 225, and con sists in matching the performance of a test sampie with blends of cetane and alphamethylnaphthalene. The percent cetane in the blend with the alphamethyl-naphthalene giving the same ignition quality test performance as the fuel in question is taken as the cetane number of that fuel.

The proportion of the ignition quality improving agent to be added to the hydrocarbon fuel may range from a fraction of one percent'to the limit of solubility in the fuel, but preferably from about .025 to 5%. A gas oil boiling from about 400 F. to 700 F., or 750 F., or in general having a suitable boiling range for use as a fuel in Diesel type engines may be used as the hydrocarbon fuel. Under some circumstances, a more narrowly cut fraction such as one distilling from about 400 F. to 600 F. or from 500 F. to 700 F. may be used. Ordinarily, the hydrocarbon fuel may be said to have a boiling range above that of gasoline. v

This invention makes commercially feasible the preparation of Diesel fuels giving satisfactory engine performance from crude oils, gas oils, and residual fuels having low pour points, low A. P. I. gravities and high heat values, such as those procured from naphthene base,-asphalt base, or mixed base stocks by the addition of active diazo compounds, described, in small quantities. The burning qualities of gas oils from paraffin crudes are also enhanced by these novel addition agents.

Small quantities of the novel addition agents of this invention may be used for adapting various mixtures of hydrocarbons for use as Diesel aaaaavo fuels, including recycle stock from a cracking operation, non-parafllnic extracts, oils from destructive distillations of pyrobituminous and asphaltic materials, mixtures of these with one another or with crude petroleum fractions. Other agents for enhancing various other qualities without detracting. substantially from the ignition qualities of the fuel may be admixed, such as, oiliness agents, sludge dispersers, dyes, corrosion inhibitors, anti-oxidants, viscosity improvers, pour depressants, and gum solvents. Also, other promoters of ignition qualities may be admixed.

It is not intended that this invention be limited to the specific examples which are given merely for the sake of illustration. It is desired to claim all the novelty inherent in the invention in the appended claims as broadly as the prior art permits.

We claim:

1. A fuel for compression-ignition engines of the Diesel type, comprising essentially a hydrocarbon fuel and a small amount of an organic compound containing in the same molecule a diazo and a corboxy group to impart better ignition qualities to the fuel.

2. A fuel for compression-ignition engines of the Diesel type, comprising essentially a hydrocarbon fuel and a small amount of an organic compound containing in the same molecule a diazo and an acetoxy group to impart better ignition qualities to the fuel.

3. A fuel for compression-ignition engines of the Diesel type, comprising essentially a hydrocarbon fuel and a small amount of an organic compound containing a diazo group linked to an acetic acid radical dissolved therein to impart better ignition qualities to the fuel.

7 4. A fuel for compression-ignition engines of the Diesel type, comprising essentially a hydrocarbon fuel and a small amount of a diazo acetic ester dissolved therein to impart better ignition qualities to the fuel.

5. A fuel for compression-ignition engines of the Diesel type comprising essentially a small amount of an alkyl diazo acetate and a hydrocarbon fuel.

6. A fuel for compression-ignition engines of the Diesel type comprising essentially a hydrocarbon fuel and a small amount of ethyl diazoacetate.

PI-IARIS MILLER. GOULD H. CLOUD. 

